Located oceanside of U.S. Highway 1, at approximately mile marker 61, between Long Key (I) and Grassy Key (I).

Called by the Spanish Chinche - SP. "The Bug". DeBrahm chart (1772) shows Reynolds Island. Named Duck Kay on both Gauld (1775) and Blunt (1846) charts, as well as in the 1799 Journal of Andrew Ellicott. A derrotero, or set of sailing directions published in 1820 in Madrid has Cayo de Holandes (SP. - Dutch Key) Blunt's American Coast Pilot of 1842 has "Dutch Key, or Cayo Holandes."

This key was the site of a salt manufacturing operation in the 1820s & 1830s. Occupation of the island ceased after the hurricane of 1935 and did not resume until the key was connected to the highway by a causeway in 1953. J.W. Norie, in his Piloting Directions for the Gulf of Florida, The Bahama Bank & Islands (1828) states: "Duck Key - Some two miles long, low, rocky, & covered with mangroves; some small patches of good land with a little timber. This island formerly saltworks but they were transferred latterly to Key West, owned by Mr. Howe, who is also possessor of this Key." Hawk's Cay Resort is currently located here, and the island is sometimes known by that name.